Respiration is necessary to supply organisms with energy which help them to maintain themselves, move, excrete, grow and reproduce. The main source of energy for organisms is the radiant energy from sunlight. During photosynthesis, green plants transofrm this energy into chemical energy which is stored in the organic foods (products of photosynthesis). This stored chemical energy is obtained by orgnisms (animals) by feeding on green plants or on other animals.
HOW DOES THIS STORED CHEMICAL ENERGY RELEASED FROM THE FOOD?
since the energy is locked up in the organic food molecules, an organism will have to oxidise them. This process of oxidation which occurs within every living cells of animals (aw well as plants) is called respiration.
IMPORTANT:
When students were asked about their pre-conceptions about respiration, the common misconception was that respiration is thought to be a scientific name for breathing.... NO... Totally WRONG!..... But breathing does help indirectly by bringing in oxygen into your body.....
DEFINITION OF RESPIRATION IN GENERAL:
Respiration is the oxidation of food substances (mainly glucose) with the release of energy in living cells.
Note: Do Not use BURNING or BREAK DOWN...... Stick to OXIDATION....... and it is very important for you to remember that respiration occurs within living cells and where in the cells? The MITOCHONDRIA.....
Respiration can be of two forms: AEROBIC RESPIRATION and ANAEROBIC RESPIRATION.
AEROBIC RESPIRATION
Aerobic respiration is defined as the oxidation of food substances in the presence of oxygen with the release of a large amount of energy and carbon dioxide and water as the waste products.
Aerobic respiration can be represented by the following equation.
C6H12O6 + 6O2 --> 6CO2 + 6H2O + Energy
How much energy? 17.1kJ/g of glucose.
The process shown by the above equation involves many enzyme-catalysed reactions. The enzymes for each of these enzyme-catalysed reactions are found in the mitochondria. Hence mitochondria are important in respiration. In fact it is the site where respiration occurs.
USES OF ENERGY PRODUCED AS A RESULT OF AEROBIC RESPIRATION
ANAEROBIC RESPIRATION
Anaerobic respiration is defined as the oxidation of food substances in the absence of oxygen with the release of a small amount of energy.
ANAEROBIC RESPIRATION IN YEAST (FERMENTATION)
Yeast is a kind of fungi which is used in bread making. Yeast cells oxidise glucose during frementation. The products is ethanol which is an alcohol. For this reason, anaerobic respiration is yeast is also called alcoholic fermentation. Anaerobic respiration is yeast can be represented by the following equation:
C6H12O6 --> 2C2H5OH + 2CO2 + Energy
How much energy is released? 1.17kJ/g glucose.
Less energy is released because the alcohol molecule is relatively large and still contains a conisderable amount of chemical energy. The small amount of energy released is only enough for the yeast to survive.
(Note: the carbon dioxide produced as the waste products actually helps in raising the bread dough thus making the bread fluffy)
(Note: wine is also made in a similar way. The glucose in grapes is oxidised in the same way)
ANAEROBIC RESPIRATION IN MUSLCES
Normally muscle cells respire aerobically (using oxygen gas). But in certain circumstances, where oxygen is not available for a very short period of time, these cells need to respire anaerobically (without oxygen gas). This usually occurs during a vigorous or strenous exercise such as sprinting in a 100m race.
What actually happens here?
How much energy is released? 0.83kJ/g glucose
HOW DOES THIS STORED CHEMICAL ENERGY RELEASED FROM THE FOOD?
since the energy is locked up in the organic food molecules, an organism will have to oxidise them. This process of oxidation which occurs within every living cells of animals (aw well as plants) is called respiration.
IMPORTANT:
When students were asked about their pre-conceptions about respiration, the common misconception was that respiration is thought to be a scientific name for breathing.... NO... Totally WRONG!..... But breathing does help indirectly by bringing in oxygen into your body.....
DEFINITION OF RESPIRATION IN GENERAL:
Respiration is the oxidation of food substances (mainly glucose) with the release of energy in living cells.
Note: Do Not use BURNING or BREAK DOWN...... Stick to OXIDATION....... and it is very important for you to remember that respiration occurs within living cells and where in the cells? The MITOCHONDRIA.....
Respiration can be of two forms: AEROBIC RESPIRATION and ANAEROBIC RESPIRATION.
AEROBIC RESPIRATION
Aerobic respiration is defined as the oxidation of food substances in the presence of oxygen with the release of a large amount of energy and carbon dioxide and water as the waste products.
Aerobic respiration can be represented by the following equation.
C6H12O6 + 6O2 --> 6CO2 + 6H2O + Energy
How much energy? 17.1kJ/g of glucose.
The process shown by the above equation involves many enzyme-catalysed reactions. The enzymes for each of these enzyme-catalysed reactions are found in the mitochondria. Hence mitochondria are important in respiration. In fact it is the site where respiration occurs.
USES OF ENERGY PRODUCED AS A RESULT OF AEROBIC RESPIRATION
- Synthesis of proteins from amino acids
- Cell division and therefore growth
- Heartbeat
- Respiratory movements
- Muscular contractions
- Active transport (absorption of glucose and amino acids by the villi in the small intestine is by active tranport. So does absorption of mineral salts by the root hair cells)
- Transmission of nerve impulses
ANAEROBIC RESPIRATION
Anaerobic respiration is defined as the oxidation of food substances in the absence of oxygen with the release of a small amount of energy.
ANAEROBIC RESPIRATION IN YEAST (FERMENTATION)
Yeast is a kind of fungi which is used in bread making. Yeast cells oxidise glucose during frementation. The products is ethanol which is an alcohol. For this reason, anaerobic respiration is yeast is also called alcoholic fermentation. Anaerobic respiration is yeast can be represented by the following equation:
C6H12O6 --> 2C2H5OH + 2CO2 + Energy
How much energy is released? 1.17kJ/g glucose.
Less energy is released because the alcohol molecule is relatively large and still contains a conisderable amount of chemical energy. The small amount of energy released is only enough for the yeast to survive.
(Note: the carbon dioxide produced as the waste products actually helps in raising the bread dough thus making the bread fluffy)
(Note: wine is also made in a similar way. The glucose in grapes is oxidised in the same way)
ANAEROBIC RESPIRATION IN MUSLCES
Normally muscle cells respire aerobically (using oxygen gas). But in certain circumstances, where oxygen is not available for a very short period of time, these cells need to respire anaerobically (without oxygen gas). This usually occurs during a vigorous or strenous exercise such as sprinting in a 100m race.
What actually happens here?
- At the beginning of an exercise, the muscle cells first respire aerobically
- Soon the amount of oxygen available in the muscle cells becomes depleted
- Despite the increased breathing rate and heart beat, oxygen cannot be transpoted to the mucles fast enough to be used for respiration
- Under this circumstance, the muscle cells then respire anaerobically to continue producing energy (though only a small amount is produced)
- In the absence of oxygen in the muscle cells, the glucose is converted to lactic acid together with a comparativley small amount of energy
How much energy is released? 0.83kJ/g glucose
- During the exercise period the muslces is said to incur an oxygen debt (more oxygen is used up than can be supplied by the blood)
- This "debt" is "paid" by fast and deep breathing in the recovery period after the exercise
- During the recovery period, 1/6 of the lactic acid produced during the exercise is oxidised aerobically into carbon dioxide and water to produce enough energy to convert 5/6 of the lactic acid back into glucose
- The glucose formed this way is then used in the normal aerobic respiration to relaease a large amount of energy
- Note: Sometimes, individual experiences muscle cramp. This is due to an accumulation of lactic acid in their muslces. If the level of lactic acid exceeds the individual tolerance level (depending on how fit the individual is), muslces stop contracting and cramp occurs)
